Fighting Diseases

• Preventing Disease


  Pathogents can make life very difficult, but there are lots of things we can do to protect ourselves
• The Spread of Disease Can Be Reduced or Prevented


  1. Being Hygienic

  2. Destroying Vectors

  3. Isolating Infected Individuals

  4. Vaccination
• Being Hygienic


  Using simple hygiene measures can prevent the spread of disease. Doing things like washing your hands thoroughly before preparing food or after you've sneezed can stop you infecting another person.
• Destroying Vectors


  By getting rid of the organisms that spread disease, you can prevent the disease from being passed on. Vectors that are insects can be killed using insecticides or by destroying their habitat so that they can no longer breed.
• Isolating Infected Individuals


  If you isolate someone who has a communicable disease, it prevents them from passing it on to anyone else.
• Vaccination


  Vaccinating people and animals against communicable diseases means that they can't develop the infection and then pass it on to someone else.
• For example, in the UK, most poultry (e.g. chickens and turkeys) is given a vaccination against Salmonella. This is to control the spread of the disease.
• Features of the human body that stop pathogens getting inside

  • The skin acts as a barrier to pathogens and secretes antimicrobial substances
  • Hairs and mucus in your nose trap particles that could contain pathogens
  • The trachea and bronchi secrete mucus to trap pathogens
  • The trachea and bronchi are lined with cilia which move mucus up to the back of the throat
  • The stomach produces hydrochloric acid which kills pathogens
• White blood cells


  The most important part of your immune system. They travel around in your blood and crawl into every part of you, constantly patrolling for microbes.
• How white blood cells attack pathogens


  1. Consuming them (phagocytosis)

  2. Producing antibodies

  3. Producing antitoxins
• Antibodies


  Proteins produced by white blood cells to lock onto and destroy invading pathogens
• If the person is infected with the same pathogen again the white blood cells will rapidly produce the antibodies to kill it, so the person is naturally immune to that pathogen and won't get ill.
• Vaccination


  Involves injecting small amounts of dead or inactive pathogens which carry antigens, causing the body to produce antibodies to attack them
• If live pathogens of the same type appear after vaccination

  The white blood cells can rapidly mass-produce antibodies to kill off the pathogen, so you don't get ill.
• Pros of vaccination


  • Vaccines have helped control lots of communicable diseases
  • Big outbreaks of disease can be prevented if a large percentage of the population is vaccinated
• Cons of vaccination


  • Vaccines don't always work
  • You can sometimes have a bad reaction to a vaccine
• Painkillers


  Drugs that relieve pain but don't tackle the cause of the disease or kill pathogens
• Antibiotics


  Drugs that kill or prevent the growth of bacteria causing a problem without killing your own body cells
• Antibiotics don't destroy viruses (e.g. flu or cold viruses). Viruses reproduce using your own body cells, which makes it very difficult to develop drugs that destroy just the virus without killing the body's cells.
• Antibiotic resistance


  Bacteria can mutate to become resistant to antibiotics, meaning the resistant strains survive and reproduce
• To slow down the rate of development of resistant strains, it's important for doctors to avoid over-prescribing antibiotics and for patients to finish the whole course of antibiotics.
• Many drugs originally came from plants, which produce chemicals to defend themselves against pests and pathogens.
• Drugs developed from plant chemicals

  • Aspirin (from willow)
  • Digitalis (from foxgloves)
• Some drugs were extracted from microorganisms, like penicillin which was discovered in a mould on a Petri dish.
• Nowadays, drugs are made on a large scale in the pharmaceutical industry, often starting with a chemical extracted from a plant.
• Stages in drug testing


  1. Preclinical testing on human cells/tissues and live animals

  2. Clinical trials on healthy volunteers and patients
• Placebo


  A substance that's like the drug being tested but doesn't do anything, used to test the actual difference the drug makes
• Clinical trials are blind - the patient and doctor don't know whether they're getting the drug or the placebo, to prevent subconscious influence.
• The results of drug testing and drug trials aren't published until they've been through peer review to check the work is valid and the claims are accurate.